For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
the ISL6259 is doing its job if SMC_BC_ACOK is high and PPBUS_G3H is 8.1v. The SMC is going to tell the ISL6259 to take PPBUS_G3H from 8.1v to 8.4v when the SMC turns on. The SMC isn't turning on.
If SMC_RESET_L is 3.38v, the SMC is being told to turn on, but is not. So either the SMC is dead or there is some corrosion under it. I would give it a light reflow, if that doesn't fix replace SMC.
The spill around L6995 probably got to the PP3V42 regulator as well and caused it to send a spike of 8 or 16v to the SMC, which could've killed it.